May
be
used
to
represent
additional
information
that
is
not
part
of
the
basic
definition
of
the
element.
In
order
to
To
make
the
use
of
extensions
safe
and
manageable,
there
is
a
strict
set
of
governance
applied
to
the
definition
and
use
of
extensions.
Though
any
implementer
is
allowed
to
can
define
an
extension,
there
is
a
set
of
requirements
that
SHALL
be
met
as
part
of
the
definition
of
the
extension.

There
can
be
no
stigma
associated
with
the
use
of
extensions
by
any
application,
project,
or
standard
-
regardless
of
the
institution
or
jurisdiction
that
uses
or
defines
the
extensions.
The
use
of
extensions
is
what
allows
the
FHIR
specification
to
retain
a
core
level
of
simplicity
for
everyone.